Operational mode control of a motor

Abstract

One example is a system for controlling a motor during startup. The system includes measurement logic, pattern detection logic, and mode logic. The measurement logic monitors a back-electromotive force (BEMF) signal representing a BEMF of an electric motor and the pattern detection logic monitors this signal to detect instances of the monitored BEMF signal exhibiting a predetermined pattern. The mode logic enables control of the electric motor according to a plurality of modes of control. In some examples, the mode logic initially employs a first mode of control and switches from the first mode of control to a second mode of control in response to the pattern detection logic detecting that a BEMF signal exhibits the predetermined pattern over a plurality of commutation states.

What is claimed is: 
     
       1. A circuit device comprising:
 measurement logic operable to:
 couple to a motor to measure a property associated with motion of the motor; and 
 provide a measurement signal based on the property; 
 
 pattern detection logic coupled to the measurement logic and operable to:
 receive the measurement signal; 
 receive a pattern associated with the motion of the motor, wherein the motor operates in a plurality of commutation states during the motion and the pattern specifies a behavior of the measurement signal over a set of the plurality of commutation states and wherein the pattern specifies the behavior of the measurement signal over a set of contiguous states of the plurality of commutation states; 
 compare the measurement signal to the pattern; and 
 provide a mode control signal that specifies a mode of operation from a plurality of modes for control of the motion of the motor based on the comparison; and 
 
 control logic coupled to the pattern detection logic and the motor and operable to control the motion of the motor in the mode specified by the mode control signal. 
 
     
     
       2. The circuit device of  claim 1 , wherein the property includes back-electromotive force of the motor. 
     
     
       3. The circuit device of  claim 1 , wherein:
 the motor has a plurality of phases; 
 the behavior includes a voltage of an idle phase of the plurality of phases crossing a threshold voltage; and 
 the pattern detection logic includes:
 crossing detection logic operable to detect the voltage of the idle phase crossing the threshold voltage in the measurement signal; and 
 a counter operable to count a number of occurrences of the voltage of the idle phase crossing the threshold voltage in the measurement signal. 
 
 
     
     
       4. The circuit device of  claim 3 , wherein the threshold voltage is a midpoint between a maxima and minima of the voltage. 
     
     
       5. The circuit device of  claim 3 , wherein the threshold voltage is zero volts. 
     
     
       6. The circuit device of  claim 1 , wherein the control logic is operable to control the motor to operate in an open-loop mode of operation prior to detection of the pattern and to operate in a closed-loop mode of operation after detection of the pattern. 
     
     
       7. The circuit device of  claim 6 , wherein the closed-loop mode of operation is based on a back-electromotive force of the motor. 
     
     
       8. A circuit device comprising:
 pattern detection logic operable to:
 couple to measurement logic to receive a measurement signal representing a measurement related to motion of a motor; 
 compare the measurement signal to a pattern; and 
 couple to a mode control logic to provide a mode control signal that specifies a mode of operation for control of the motion of the motor based on the comparison, wherein:
 the motor operates in a plurality of commutation states during the motion; 
 the pattern specifies a behavior of the measurement signal; 
 the pattern detection logic includes counter logic operable to count a number of occurrences of the behavior of the measurement signal over a set of the plurality of commutation states; and 
 the pattern detection logic is operable to provide the mode control signal that specifies the mode of operation based on the count of the number of occurrences of the behavior of the measurement signal over the set of the plurality of commutation states. 
 
 
 
     
     
       9. The circuit device of  claim 8 , wherein:
 the motor has a plurality of phases; 
 the behavior includes a voltage of an idle phase of the plurality of phases crossing a threshold voltage; and 
 the counter logic is operable to count a number of occurrences of the voltage of the idle phase crossing the threshold voltage in the measurement signal. 
 
     
     
       10. The circuit device of  claim 9 , wherein the pattern detection logic further includes crossing detection logic coupled to the counter logic and operable to:
 receive the measurement signal; 
 detect the voltage of the idle phase crossing the threshold voltage in the measurement signal; and 
 provide a crossing detection signal to the counter logic upon detection of the voltage of the idle phase crossing the threshold voltage. 
 
     
     
       11. The circuit device of  claim 9 , wherein the threshold voltage is a midpoint between a maxima and minima of the voltage. 
     
     
       12. The circuit device of  claim 8 , wherein the set of the plurality of commutation states over which the counter logic is operable to count the number of occurrences of the behavior is a set of consecutive commutation states. 
     
     
       13. The circuit device of  claim 8 , wherein the measurement signal represents a back-electromotive force measurement of the motion of the motor. 
     
     
       14. The circuit device of  claim 8 , wherein the pattern detection logic is operable to provide the mode control signal to specify an open-loop mode of operation prior to detection of the pattern and to specify a closed-loop mode of operation after detection of the pattern. 
     
     
       15. The circuit device of  claim 14 , wherein the closed-loop mode of operation controls the motion of the motor based on the measurement signal. 
     
     
       16. A method, comprising:
 receiving a measurement signal associated with motion of a motor during a plurality of commutation states of the motor; 
 receiving a pattern that specifies a behavior over a subset of the plurality of commutation states of the motor, wherein the pattern specifies a threshold number of contiguous commutation states; 
 comparing the measurement signal to the pattern; 
 selecting a mode of operation for the motor based on the comparing of the measurement signal to the pattern, wherein the selecting of the mode of operation is based on detecting the behavior in at least the threshold number of contiguous commutation states; and 
 operating the motor in the selected mode of operation. 
 
     
     
       17. The method of  claim 16 , wherein the measurement signal is based on a back-electromotive force of the motor. 
     
     
       18. The method of  claim 16 , wherein the selecting selects an open-loop mode of operation prior to detecting the behavior and a closed-loop mode of operation after detecting the behavior.